Fe Chelates Research Articles

Novel Fe (III), Cu (II), and Zn (II) Chelates of Organoselenium‐Based Schiff Base: Design, Synthesis, Characterization, DFT, Anticancer, Antimicrobial, and Antioxidant Investigations

Novel Fe (III), Cu (II), and Zn (II) Chelates of Organoselenium‐Based Schiff Base: Design, Synthesis, Characterization, DFT, Anticancer, Antimicrobial, and Antioxidant Investigations

Design principles for selective nitrogen adsorption via chelation of metals in metal organic frameworks

Designing porous materials with N2 selectivity performance is highly attractive for the efficient removing N2 from natural gas. However, selectively capturing N2 over CH4 is challenging due to their similar physical properties. In this work, we proposed achieving N2 selectivity adsorption over CH4 by chelating Fe2+ sites on the ligands of MOFs. The significant enhancement of N2/CH4 separation by Fe chelation was demonstrated using multiscale simulations, including quantum mechanics calculations, force field development, and GCMC simulations. Specifically, Fe chelated MOFs can achieve a record-high N2 adsorption capacity while maintaining N2/CH4 selectivity comparable to that of current benchmark N2 selective capture MOFs. Moreover, based on simulation data from 331 Fe chelated MOFs with various topologies, we quantified the structure-properties relationships for N2/CH4 separation using Fe chelated MOFs through interpretable machine learning, which provides precise and intuitive guidance for designing novel adsorbents for selective N2 adsorption.

Exogenous deferoxamine mesylate suppresses iron-dependent ferroptosis in postharvest fruit rot of blueberry caused by Alternaria alternata and Fusarium fujikuroi

Plant development relies heavily on regulated cell death, which is crucial for specific plant responses to biological stresses. Ferroptosis, an iron-dependent, oxidative, and non-apoptotic cell death form, has been recently discovered in animal cells. In this study, we investigated whether a ferroptosis-like process could be relevant to cell death in postharvest fruit rot of blueberry caused by Alternaria alternata and Fusarium fujikuroi. The results showed that deferoxamine mesylate and glutathione (GSH) treated fruit showed enhanced disease resistance with lower lesion areas, whereas an opposite result was observed in hydrogen peroxide (H2O2) treatment, indicating that intracellular ferroptosis might exist in the fungal infected blueberry fruit. Compared to control, deferoxamine mesylate or GSH treatment improved chlorophyll fluorescence parameters, which contributed to the stability of photosynthesis. In terms of ferroptosis pathway in the adjacent area of infected fruit, deferoxamine mesylate suppressed an iron-dependent cell death pathway that was characterized by depletion of H2O2 and MDA and accumulation of GSH, as well as the reduction of ferrous ions and total iron ions. Meanwhile, deferoxamine mesylate could effectively delay the decrease rate of unsaturation value and key phospholipids of fungi infected fruit during storage, which possibly maintained the integrity of cell membrane. Due to the serious rot of the lesion area, the peroxidation of membrane lipids was severe, accompanied by metabolic disorders. These combined results demonstrated that deferoxamine mesylate treatment could reduce Fenton reaction by chelating Fe2+ and avoid excessive accumulation of reactive oxygen species (ROS), suppress iron-dependent ferroptosis, thereby maintaining fruit quality and reducing postharvest diseases.

Synthesis, Structural Characterization, Anticancer, Antimicrobial, Antioxidant, and Computational Assessments of Zinc(II), Iron(II), and Copper(II) Chelates Derived From Selenated Schiff Base

ABSTRACTNovel selenated azomethine ligand (MSeOH) and its Zn(II), Fe(II), and Cu(II) chelates were synthesized. Their chemical structures were confirmed by molar conductivity, thermal analysis, X‐ray diffraction, IR, NMR, and MS spectroscopic techniques. The antitumor and antimicrobial properties were evaluated against various mammalian cells and pathogenic strains. Furthermore, the antioxidant activities were also assessed using DPPH and SOD bioassays. To gain a deeper understanding of the molecular structure and electronic properties of these complexes, a density functional theory (DFT) study was conducted. The parameters examined in this study provide valuable insight into the bonding, electronic properties, reactivity, and polarity of the compounds under investigation. The biological and theoretical results point to promising activities of the selenated ligand and its complexes.

Protein glycosylation inhibitory effects and mechanisms of phloretin and phlorizin

The anti-glycation potential and mechanism of phloretin and phlorizin were investigated in the study. In the methylglyoxal (MGO)-human serum albumin (HSA) glycosylation system, the inhibition against fluorescent advanced glycosylation end products (AGEs) was more than 60% at 960 μM phloretin and phlorizin. They decreased carbonylation and oxidative damage of protein, protected thiol groups and secondary structure of protein and inhibited protein aggregates. Treated with 1.37 mM phloretin or phlorizin, O2−· scavenging was more than 80%, and 1 mM phloretin or phlorizin chelated 60.08% or 28.11% of Fe2+, respectively. Analysis of HPLC and LC-QqQ-MS shown phloretin captured MGO by forming adducts with MGO, with capture rates of 92.67% within 24 h. The capture rate of phlorizin to MGO was 56.40%. The anti-glycosylation mechanisms of them could include the structural protection of HSA, capture of MGO, O2−· and ·OH scavenging and chelation of Fe2+. These findings may provide a theoretical basis for the application of phloretin and phlorizin as novel anti-glycosylation agents.

Cultivating resilience: Harnessing pyoverdine-producing Pseudomonas to contrast iron deficiency in cucumber plants

Iron (Fe) deficiency in crops significantly reduces yield, impacting agricultural productivity worldwide. Synthetic Fe chelates are commonly applied as fertilizers to address this issue, but their synthetic nature and prolonged use poses environmental risks. Thus, inoculation of plant growth-promoting bacteria rises as an alternative to enhance Fe uptake in crops while minimizing reliance on synthetic chelates. This study aimed to examine the influence of Pseudomonas RMC4 inoculation and pyoverdine application on cucumber plants cultivated hydroponically under Fe deficiency conditions. Evaluations included the SPAD index, plant biomass, root morphology, Fe-chelate reductase activity, gene expression, and ionomic analysis. Following Fe deficiency, Pseudomonas RMC4 inoculation improved the SPAD index, increased dry weight, enhanced root development, and facilitated Fe acquisition mechanisms, thus, fostering the endogenous resilience of the plant to the limited Fe availability. This improvement was observed with bacterial inoculation or pyoverdine application alongside an insoluble Fe source (ferrihydrite). Overall, the results suggest the beneficial impact of Pseudomonas RMC4 inoculation in alleviating symptoms of Fe deficiency. Future studies will investigate bacterial application under field conditions to assess its potential in replacing synthetic Fe-chelates fertilizers in crop production in favor of more sustainable agriculture.

The phytosiderophore analogue proline-2′-deoxymugineic acid is more efficient than conventional chelators for improving iron nutrition in maize

ABSTRACT Iron (Fe) is an essential nutrient but has poor bioavailability because of its low solubility under conditions of high pH, such as calcareous soils. Previously, we synthesized an analogue of the natural Fe(III) chelator 2′-deoxymugineic acid secreted by graminaceous plants for efficient Fe uptake, designated as proline-2′-deoxymugineic acid (PDMA). Soil application of Fe(III)-PDMA ameliorated symptoms of Fe deficiency in rice. In the present study, we explored the potential of PDMA as Fe nutrition supplement in maize, a major graminaceous crop, and rice for comparison. In calcareous soil pots, Fe deficiency chlorosis of maize was efficiently recovered by a single application of Fe(III)-PDMA. In contrast, maize plants treated with conventional Fe(III)-chelator complexes, such as Fe(III)-ethylenediaminetetraacetic acid (EDTA) or Fe(III)-N,N′-di(2-hydroxybenzyl)ethylenediamine-N,N′-diacetic acid monohydrochloride (HBED), showed little or no recovery. Similarly, rice Fe chlorosis in calcareous soil pots was efficiently recovered by a single application of Fe(III)-PDMA, but not by other conventional Fe(III)-chelator complexes. Application of Fe(III)-PDMA was also effective in ameliorating Fe deficiency chlorosis in hydroponically grown maize seedlings; other Fe(III)-chelator complexes showed minimal or no efficacy. Addition of low concentrations of metal-free PDMA recovered Fe chlorosis of maize or rice in the presence of Fe(III)-EDTA, suggesting possible ligand exchange from EDTA to PDMA for subsequent Fe(III)-PDMA uptake by ZmYS1 and OsYSL15 transporters. Similar effects were observed with Fe(III)-HBED, which has a higher stability constant, but to a lesser extent than Fe(III)-EDTA, suggesting that ligand exchange from HBED to PDMA might be less prone to occur than for chelators with moderate stability constants, such as EDTA. Ferric-chelate reductase assays of maize roots showed substantial reduction of Fe(III)-PDMA, but this reduction activity was not increased under Fe-deficient condition. These results suggested that PDMA is an efficient reagent for improvement of Fe nutrition in graminaceous crops, including maize, because of suitability of Fe(III)-PDMA as a substrate for chelation-based Fe uptake systems.

Synthesis and toxicity of monothiooxalamides against human red blood cells, brine shrimp (Artemia salina), and fruit fly (Drosophilamelanogaster)

A new family of monothiooxalamides derived from 2-aminobenzimidazole was synthesized, and their structures were confirmed by 1H and 13C one-dimensional and 2D NMR experiments (COSY, HSQC, and HMBC). The antioxidant capacity was evaluated by free radical scavenging assays: 1,1-diphenyl-2-picrylhydrazyl (DPPH•), 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS•+), ferric reducing antioxidant power (FRAP), oxygen radical absorbance capacity (ORAC), and the Fe(II) chelating ability. Our work group has previously reported the synthesis and antioxidant activity of monothiooxalamides derived from 2-aminopyridine (I). In this study, the in vitro hemolytic activity of compounds from the 2-aminopyridine (I) and 2-aminobenzimidazole (II) families was evaluated against human red blood cells (RBCs). The concentration at which monothiooxalamides showed no hemolytic activity was chosen to assess their ability to inhibit free radical-induced membrane damage in human RBCs, acute toxicity in brine shrimp, and in vivo toxicity against Drosophila melanogaster. Compounds with morpholine fragments (1g, 1h, 2g, and 2h) showed time- and concentration-dependent protective effects against radical-induced oxidative hemolysis. Moreover, they had the lowest acute toxicity in the brine shrimp lethality assay and a significant increase in chelating activity compared with the other molecules. In particular, monothiooxalamide 2g showed lower toxicity and can be considered for further biological screening and application trials.

Synthesis and characterization of new 4-amino-5-methyl-4H-1,2,4-triazole-3-thiol (MMTP) Schiff base for spectrophotometric detection of iron(III) and copper(II) ions in laboratory and different water samples: A biological and molecular docking exploration

New spectrophotometric techniques were introduced for the determination of Fe(III) and Cu(II) in many different analyzed samples. The concentrations of Fe(III) and Cu(II) ions were measured in the existence of a novel Schiff base (Z)-6-(3-mercapto-5-methyl-4H-1,2,4-triazol-4-ylimino)-2-thioxotetrahydropyrimidin-4(1H)-one (MMTP). The new chelates were formed rapidly at the room temperature at 510 and 550 nm in presence of triton X-100 and CPB surfactants for Fe(III) and Cu(II), respectively. Linear calibrated graphs were obtained at concentration ranges of 1.0–130 µg mL-1 for Fe(III) and 0.5–90 µg mL-1 for Cu(II). LOD were calculated to be 1.05, 1.98 µg mL-1 and LOQ were 3.18 and 6.02 µg mL-1 for Fe(III) and Cu(II), respectively. A large number of foreign ions were not interfering in the present method. The stoichiometric composition of the chelates was studied by molar ratio and job´s methods to be found 1:2 (metal ion: ligand) ratio. The Fe(III) and Cu(II) solid chelates were prepared and characterized using IR, UV–Vis., 1HNMR , 13CNMR TG-DTG, and XRD spectroscopy. The IR spectral revealed that MMTP chelated as a bidentate ligand via NO atoms. Thermal analysis revealed the decomposition mechanism of MMTP and its chelates. A suggested octahedral geometry encompasses all of the chelates. The UV–visible spectra and magnetic moment analyses confirm the octahedral geometrical geometries. The band gap (Eg) values are 1.53 and 1.56 for Fe(III) and Cu(II) respectively. The smallest band gaps imply that these chelates are semiconductors belonging to solar materials. The in-vitro antioxidant activity of the individual chelates was evaluated using the DPPH radical scavenging assay. All compounds showed antioxidant activity with IC50 values of 0.316, 0.186 and 0.124 mg/mL for MMTP, Fe(III) and Cu(II), respectively. MMTP and its chelates were tested for their antimicrobial activity against various types of bacteria and fungi using the disc diffusion method. The Cu(II) complex showed the greatest biological activity.

Iron Chelation in Soil: Scalable Biotechnology for Accelerating Carbon Dioxide Removal by Enhanced Rock Weathering.

Enhanced rock weathering (EW) is an emerging atmospheric carbon dioxide removal (CDR) strategy being scaled up by the commercial sector. Here, we combine multiomics analyses of belowground microbiomes, laboratory-based dissolution studies, and incubation investigations of soils from field EW trials to build the case for manipulating iron chelators in soil to increase EW efficiency and lower costs. Microbial siderophores are high-affinity, highly selective iron (Fe) chelators that enhance the uptake of Fe from soil minerals into cells. Applying RNA-seq metatranscriptomics and shotgun metagenomics to soils and basalt grains from EW field trials revealed that microbial communities on basalt grains significantly upregulate siderophore biosynthesis gene expression relative to microbiomes of the surrounding soil. Separate in vitro laboratory incubation studies showed that micromolar solutions of siderophores and high-affinity synthetic chelator (ethylenediamine-N,N'-bis-2-hydroxyphenylacetic acid, EDDHA) accelerate EW to increase CDR rates. Building on these findings, we develop a potential biotechnology pathway for accelerating EW using the synthetic Fe-chelator EDDHA that is commonly used in agronomy to alleviate the Fe deficiency in high pH soils. Incubation of EW field trial soils with potassium-EDDHA solutions increased potential CDR rates by up to 2.5-fold by promoting the abiotic dissolution of basalt and upregulating microbial siderophore production to further accelerate weathering reactions. Moreover, EDDHA may alleviate potential Fe limitation of crops due to rising soil pH with EW over time. Initial cost-benefit analysis suggests potassium-EDDHA could lower EW-CDR costs by up to U.S. $77 t CO2 ha-1 to improve EW's competitiveness relative to other CDR strategies.

Novel meroterpene-like compounds inhibit ferroptosis through Fe2+ chelation

Colorectal cancer (CRC) is the third most common type of cancer in the world. It is characterized by complex crosstalk between various signaling pathways, as a result of which it is highly challenging to identify optimal therapeutic targets and design treatment strategies. In this study, we tested the effect of 700 compounds on the CRC cell line HT-29 by using the sulforhodamine B assay and screened out 17 compounds that exhibited high toxicity (indicated by an inhibition rate of ≥75 % when applied at a concentration of 10 µM) against the HT-29 cell line. Next, we investigated the mechanisms underlying the effects of these 17 highly toxic compounds. The results of ferroptosis analysis and electron microscopy showed that compounds 575 and 578 were able to significantly reverse RSL3-induced increase in ferroptosis, while compound 580 had a less pronounced ferroptosis-regulating effect. In subsequent experiments, western blotting showed that compounds 575, 578, and 580, which belong to a class of meroterpene-like compounds that affect ferroptosis, do not induce autophagy or apoptosis in the CRC cell line. Instead, Fe2+ chelation experiments showed that these three compounds can serve as iron chelators by chelating Fe2+ at a 1:1 (chelator: Fe2+) ratio. Specifically, the aldehyde and hydroxyl groups of the benzene ring in these compounds may chelate Fe2+, thus reducing Fe2+ levels in cells and inhibiting ferroptosis. These results indicate that these novel meroterpene-like compounds are potential therapeutic small-molecule candidates for targeting ferroptosis in tumors.

Quality- and Health-Promoting Compounds of Whole Wheat Bread with the Addition of Stale Bread, Cornmeal, and Apple Pomace.

The aim of this study was to evaluate the effect of extruded preparations on the bioactive and nutritional properties, vitamin B content, volatile compound profile, and quality of whole wheat bread. Extruded preparations based on stale bread (secondary raw materials) and apple pomace (byproducts) were used as bread additives. It was found that the preparations did not enrich the bread in protein but in health-promoting compounds, especially gallic acid, protocatechuic acid, caffeic acid, p-coumaric acid, rutin, quercetin, and B vitamins. Extruded preparations had a positive effect on the quality of the bread produced, such as yield and cohesiveness, and gave it a pleasant aroma. It was shown that among all the examined bread samples with added extruded preparations of stale bread, the cornmeal and apple pomace bread samples with 15% extruded preparation (containing 55% cornmeal, 30% stale bread, and 15% apple pomace) had sufficient nutritional value, the highest amounts of gallic acid, protocatechuic acid, p-coumaric acid, caffeic acid, rutin, and quercetin; medium amounts of ellagic acid; high antioxidant activity determined in vitro using four methods (by DPPH, ABTS, power (FRAP), and Fe(II) chelating assays); adequate quality; and significant amounts of vitamins, especially B1, B2, and B3. This type of extruded preparation should utilize apple pomace, which is a byproduct, and stale bread, which is a secondary waste. Such a combination is an excellent low-cost, easy, and prospective solution for the baking industry that could be applied to obtain bread with elevated nutritional value and enhanced health potential, as proven in this publication.

Kinetic Isotope Effects During Reduction of Fe(III) to Fe(II): Large Normal and Inverse Isotope Effects for Abiotic Reduction and Smaller Fractionations by Phytoplankton in Culture

AbstractIron stable isotopes (δ56Fe) are a useful tool for studying Earth processes, many of which involve redox transformations between Fe(III) and Fe(II). Here, we present two related experimental efforts, a study of the kinetic isotope effects (KIEs) associated with the reduction of Fe(III)‐ethylenediaminetetraacetic acid (EDTA) to Fe(II), and measurements of the biological fractionation of Fe isotopes by phytoplankton in culture. Reductants tested were ascorbate, hydroxylamine, Mn(II), dithionite, and photoreduction at pH between 5 and 9 and temperatures from 0 to 100°C. Isotope fractionations were very large, and included both normal and inverse KIEs, ranging from −4‰ to +5‰. Experiments were reproducible, yielding similar results for triplicate experiments run concurrently and for experiments run weeks apart. However, fractionations were not predictable, without a clear relationship to reaction rate, temperature, pH, or the reductant used. Acquisition of Fe by eukaryotic phytoplankton also often involves the reduction of Fe(III) to Fe(II). Several species of diatoms and a coccolithophore were tested for Fe isotope fractionation in culture using EDTA, NTA, and DFB as Fe(III) chelating ligands, yielding fractionations from −1.3‰ to +0.6‰. Biological isotope effects were also unpredictable, showing no clear relationship to species, growth rate, or Fe concentration. Variability in Fe isotope fractionation observed in culture may be explained in part by the sensitivity of KIEs. This work has implications for the industrial purification of isotopes, interpretation of natural δ56Fe, and the use of Fe isotopes as a tracer Fe source and biological processes in the ocean and other natural systems.

One-step high efficiency separation of prolyl endopeptidase from Aspergillus niger and its application

Prolyl endopeptidase from Aspergillus niger (An-PEP) is an enzyme that recognizes C-terminal peptide bonds of amino acid chains and cleaves them by hydrolysis. An aqueous two-phase system (ATPS) was used to separate An-PEP from fermentation broth. Through single factor experiments, the ATPS containing 16 % (w/w) PEG2000 and 15 % (w/w) (NH4)2SO4 at pH 6.0 obtained the recovery of 79.74 ± 0.16 % and the purification coefficient of 7.64 ± 0.08. It was then used to produce soy protein isolate peptide (SPIP) by hydrolysis of soy protein isolate (SPI), and SPIP-Ferrous chelate (SPIP-Fe) was prepared with SPIP and Fe2+. The chelation conditions were optimized by RSM, as the chelation time was 30 min, chelation temperature was 25 °C, SPIP mass to VC mass was two to one and pH was 6.0. The obtained chelation rate was 82.56 ± 2.30 %. The change in the structures and functional features of SPIP before and after chelation were investigated. The FTIR and UV–Vis results indicated that the chelation of Fe2+ and SPIP depended mainly on the formation of amide bonds. The fluorescence, SEM and amino acid composition analysis results indicated that Fe2+ could induce and stabilize the surface conformation and change the amino acid distribution on the surfaces of SPIP. The chelation of SPIP and Fe2+ resulted in the enhancement of radical scavenging activities and ACE inhibitory activities. This work provided a new perspective for the further development of peptide-Fe chelates for iron supplement.

Potential Role of Bioactive Compounds: In Vitro Evaluation of the Antioxidant and Antimicrobial Activity of Fermented Milk Thistle

The group of innovative ingredients in cosmetic preparations includes bio-ferments (Bs), which are characterized by high bioactivity and biocompatibility, and one of the plants rich in bioactive compounds that has a beneficial effect on the skin and the body is Silybum marianum. Bio-ferments obtained from this plant are becoming increasingly useful as active ingredients in cosmetics. In the present study, four different bio-ferments were obtained by fermentation of pomace (B-P), extract (B-E), oil (B-O), and seeds (B-S) of milk thistle. Their biodegradability (%B), total polyphenols content (Folin–Ciocalteu method), and antimicrobial, antioxidant (DPPH, ABTS, and FRAP methods), chelating (Fe2+ ions), and reduction (Cu2+ and Fe3+ ions) properties, as well as the acidity, were evaluated. The contact angle using the sessile drop method was assessed to investigate bio-ferments’ impact on skin wettability. Finally, the content of selected phenolic acids in the Bs was evaluated using the HPLC method, while the lactic acid (LA) content was assessed using the GC-MS method. All bio-ferments were characterized by high polyphenols content (13.56 ± 0.10–15.28 ± 0.12 mmol GA/L B), chelating (0.08 ± 0.01–0.17 ± 0.01 mmol Fe2+/L B) and antioxidant activity (DPPH method, 2.41 ± 0.01–3.53 ± 0.01 mmol Tx/L B), and reducing Cu2+ and Fe3+ ions. Gallic acid, protocatechuic acid, caffeic acid, neochlorogenic acid, coumaric acid, and LA were identified in Bs. The most increased antibacterial activity for B-P was observed for a strain of Staphylococcus aureus (MIC = 250 μL/mL) and Pseudomonas aeruginosa (MIC = 250 μL/mL). Simultaneously, B-S demonstrated the highest inhibitory effects against Escherichia coli (MIC = 125 μL/mL), emphasizing the varied antimicrobial profiles of these bio-ferments against different bacterial strains. Research on aerobic biodegradation demonstrated a high level of degradation (%B = 60 ± 1–65 ± 3), and all Bs were categorized as readily degradable according to the OECD classification.

Rigid Fe(III) Chelate with Phosphonate Pendants: A Stable and Effective Extracellular MRI Contrast Agent.

A novel Fe(III) complex, Fe-tBPCDTA, was synthesized and explored as a potential contrast agent for MRI. Compared to established agents like Fe-EDTA and Fe-tCDTA, Fe-tBPCDTA exhibited moderate relaxivity (r1 = 1.17 s-1·mmol-1) due to its enhanced second-sphere mechanism. It also displayed improved kinetic inertness, lower cytotoxicity, and enhanced redox stability. In vivo studies demonstrated its function as an extracellular fluid agent, providing tumor contrast comparable to that of Gd-DTPA at a higher dosage. Complete renal clearance occurred within 24 h. These findings suggest Fe-tBPCDTA as a promising candidate for further development as a safe and effective extracellular MRI contrast agent.

Optimization of oxalic acid treatment for ulvan extraction from Ulva linza biomass and its potential application as Fe(III) chelator

This study investigated the use of oxalic acid as an eco-friendly compound for extracting ulvan from Ulva linza biomass. The concentration of oxalic acid, temperature, and period of extraction were optimized using Box-Behnken design in response of ulvan yield, molecular weight (MW), sulphate content, uronic acid content, purity ratio (total sugars/total phenolics and proteins), and Fe(III) chelation properties. Under the optimized conditions (1.7 % w/v oxalic acid, 64 °C, and 2.63 h), ulvan yield, MW, sulphate content, uronic acid content, and purity ratio were 29.90 % (w/w), 32.22 kDa, 11.01 % (w/w), 8.12 % (w/w), and 12.84, respectively. The optimized ulvan exhibited good Fe(III) chelation of 18.58 % (w/w). The synthesized Fe-ulvan complex released approximately 73 % of the chelated Fe(III) under in vitro simulated gastro-intestinal conditions. Furthermore, both ulvan and Fe-ulvan complex exhibited potent antioxidant properties. FT-IR analysis confirmed the fundamental role played by hydroxyl, carboxyl and sulphate groups in the coordination of Fe(III). Furthermore, MW, MW/sulphate ratio, and MW/uronic acid ratio should be low to enhance the Fe(III) chelation properties of ulvan. The results of the present study shed light on the use of oxalic acid as a simple and environmentally-benign treatment for ulvan extraction, especially for the recovery of low MW ulvan with high yield and good Fe(III)-binding properties.

Biological properties of LMW-peptide fractions from apricot kernel protein: Nutritional, antibacterial and ACE-inhibitory activities

In this study, angiotensin-converting enzyme (ACE) inhibitory, antioxidant and antibacterial activities, and nutritional quality of low molecular weights (LMWs) peptide fractions (PFs) from apricot-kernel (Prunus armeniaca cv. Tabarzeh) with PFs <3, 3–10, 10–30 and 30–100 kDa were investigated. The ratio of essential to total (E/T) amino acids (∼34.5 %) and PER value (1.8–1.9) indicated the high nutritional and digestibility of peptide fractions. Antioxidant indices were affected by enzymatic hydrolysis, molecular weight (Mw) and concentration of peptides. In general, the highest inhibition of DPPH− (89.2 %), ABTS+ (93.1 %), TEAC (2.52 mM), OH• (78.1 %), NO• (70.4 %), total antioxidant activity (2.01), reducing power (1.27), ACE inhibitory (75.1 %), chelation of Fe2+ (90.2 %) and Cu2+ (40.2 %) metal-ions were related to low Mw fractions (PF-3 and PF-10). The hydrolysates and primary protein showed enhanced antibacterial effects against Escherichia coli and Bacillus cereus with diameter of inhibition zones of 17 and 14 mm, respectively. Overall, apricot-kernel peptides can be considered as a nutrient source, natural antioxidant and preservative with ACE-inhibitory effect in dietary supplements and food formulations.

Computational insight into the Fe(II) chelation of Hibiscetin for the enhanced antioxidant activity

Computational insight into the Fe(II) chelation of Hibiscetin for the enhanced antioxidant activity

Near UV Photodegradation Mechanisms of Amino Acid Excipients: Formation of the Carbon Dioxide Radical Anion from Aspartate and Fe(III).

Carbon dioxide radical anion (•CO2-) is a powerful reducing agent that can reduce protein disulfide bonds and convert molecular oxygen to superoxide. Therefore, the generation of •CO2- can be detrimental to pharmaceutical formulations. Iron is among the most prevalent impurities in formulations, where Fe(III) chelates of histidine (His) can produce •CO2- upon exposure to near-UV light (Zhang and Schöneich, Eur. J. Pharm. Biopharm. 2023, 190, 231-241). Here, we monitor by spin-trapping in combination with electron paramagnetic resonance spectroscopy and/or high-performance liquid chromatography-mass spectrometry analysis the photochemical formation of •CO2- for a series of common amino acid excipients, including arginine (Arg), methionine (Met), proline (Pro), glutamic acid (Glu), glycine (Gly), aspartic acid (Asp), and lysine (Lys). Our results indicate that in the presence of Fe(III), Asp, and Glu produce significant yields of •CO2- under photoirradiation with near-UV light. Notably, Asp demonstrates the highest efficiency of •CO2- generation compared with that of the other amino acid excipients. Stable isotope labeling indicates that •CO2- exclusively originates from the α-carboxyl group of Asp. Mechanistic studies reveal two possible pathways for •CO2- formation, which involve either a β-carboxyl radical or an amino radical cation intermediate.